Irradiation of S-nitrosoglutathione (GSNO) with light ( = 550 nm) resulted in the homolytic decomposition of GSNO to generate glutathionyl radical (GS ) and nitric oxide, which were monitored by ESR spectroscopy. Inclusion of Rose Bengal (RB) resulted in a 9-fold increase in the quantum yield for nitric oxide production and also an increase in the rate of thiyl radical formation. The bimolecular rate constant for the interaction of triplet RB with GSNO has been estimated to be approximately 1.2 109 M-1 s-1 by competition with oxygen. Hematoporphyrin (HP) also enhanced the rate of nitric oxide production by 2-3-fold. 2-Methyl-2-nitrosopropane (MNP) decomposed on irradiation ( = 660 nm) to form nitric oxide and tert-butyl radical. Aluminum phthalocyanine tetrasulphonate enhanced the rate of decomposition of MNP by 10-fold. These studies show that photosensitizers enhance the release of nitric oxide from donor compounds.